Wheelchairs are well known forms of transportation that increase the mobility of the physically impaired. Wheelchairs are typically relatively small, single-person conveyances that generally comprise a seat supported by a frame which, in turn, is supported by two opposed drive wheels and two front casters.
The wheelchair occupant's center of gravity is generally positioned close to the drive wheels to permit the wheelchair occupant to maneuver the wheelchair with greater ease. The wheelchair occupant's center of gravity may be shifted in a number of ways. The drive wheels may be cambered so that the distance between the drive wheels at ground level is greater than the distance between the drive wheels at the seat. In addition to cambering the drive wheels, adjusting the position of the drive wheels relative to the wheelchair frame may also shift the wheelchair occupant's center of gravity. For example, the drive wheels may be moved forward or backward, or may be raised or lowered, relative to the wheelchair frame to shift the wheelchair occupant's center of gravity.
Adjusting the wheelchair seat relative to the wheelchair frame may also shift the center of gravity of the wheelchair occupant. In addition to shifting the center of gravity of the wheelchair occupant, adjusting the wheelchair seat may improve the orientation of the arms and hands of the wheelchair occupant relative to the drive wheels. Improving the orientation of the arms and hands of the wheelchair occupant relative to the drive wheels enables the occupant of the wheelchair to propel the wheelchair with greater comfort and increased efficiency. Adjusting the wheelchair seat periodically also reduces the risk of tissue trauma suffered by the wheelchair occupant by reducing the constant pressure between the wheelchair occupant's skin and the wheelchair, and particularly, the wheelchair seat.
Adjusting the position of the drive wheels relative to the wheelchair frame can be accomplished in several ways. Typically, the drive wheels are mounted for rotation on an axle, with the axle being insertable into an axle tube that is mounted on the wheelchair frame. Adjustment between the relative positions of the drive wheels and the wheelchair frame can be accomplished by moving the axle tube relative to the frame. Another means of adjusting the position of the drive wheels relative to the wheelchair frame is to move the portions of the frame housing the axle tube relative to the remainder of the wheelchair frame. It is known to have an axle bracket that can be mounted to a frame member in either a forward or rearward direction to provide longitudinal adjustability of the axle with respect to the frame.
It would be advantageous if there could be developed a simplified assembly for enabling easy adjustment of the position of wheelchair drive wheels with respect to the wheelchair frame. Such a mechanism should be easy to assemble and disassemble for rapid adjustment of the wheelchair drive wheels, and should provide a wide margin of adjustment. Further, the mechanism should be simple in construction for long service life, easy installation and low manufacturing cost.